1. Field of the Invention
This invention is directed generally to apparatus and methods for heat regulation of cooking systems, such as a deep fat fryer, and more specifically to apparatus and methods for heat regulation for use with such flyers for regulating the temperature of a transitional zone of the flyer, so as to eliminate the potential boiling of a cooking substance within the fryer.
2. Description of Related Art
Large capacity pressurized deep fat fryer cookers (referred herein as deep fat fryers, cooking devices, cookers, and the like) have been devised for cooking products in a heated and/or pressurized environment. Typically such devices comprise a cooking vessel, which may be filled with a type of cooking substance (e.g., oil or shortening) and heating devices surrounding or immersed in the vessel for heating the cooking oil. Products to be cooked are placed in the vessel, either directly or possibly contained in a wire basket, and are cooked for a desired length of time.
While such cooking devices described above provide for a relatively effective cooking environment, a problem exists with these devices. Specifically, the cooking substance (e.g., oil or shortening) used in these cooking devices has the potential to boil over the sides of the cooking vessel at certain times. This problem is linked to the amount of moisture contained within the "cracklings" found within the non-cooking zones of the cooking substance, i.e., usually toward the bottom of the vessel.
Generally, "cracklings" are pieces of breading, skin or other items which have dropped off of a food item being cooked in the fryer. For example, if fried chicken pieces are being cooked within the vessel, some of the breading applied before cooking the chicken may break away from the chicken and drift to the lower zones of the vessel. In the lower portions of the cooking vessel, the cracklings are less likely to cause degradation of the cooking substance in contact with the food products. Because moisture may be found within the cracklings, such moisture may cause the cooking substance to boil over if the cracklings become mixed with the hot oil in the upper zones of the vessel. Further, if the temperature in the bottom of the cooking vessel is too high, the cracklings may burn causing the oxidation of the cooking substance. Such oxidation reduces the useful life of the cooking substance.
Some fryers include a cooking substance filtration system to remove cracklings and other undesirable solids from the cooking substance. The fryer may include a drain and a drain valve located in the lower portion of the cooking vessel. The drain may be located above a filter tank or may be connected by appropriate conduits to the filter tank. The cooking substance may be drained from the cooking vessel into the filter tank. A pump may be used to draw the cooking substance through a filter in the filter tank and to return the filtered cooking substance to the cooking vessel.
The cold zone temperature is usually maintained by proper thermal design. However, in some fryers this thermal design is so effective that the cold zone temperature is too low. This results in difficulties in temperature regulation and in stratification of the oil in the cooking region of the cooking vessel. The cooking substance in the vessel may form three zones: a cooking zone, a transition zone, and a cold zone. U.S. Pat. No. 5,232,151 to Mercer et al. which is commonly assigned with the present application, describes a method of regulating the temperature of the cold zone of a deep fat fryer to avoid boiling over. A problem still exists with regard to regulation of temperatures in the transition zone.
If the temperature in the transition zone is not raised to a sufficient temperature (e.g., about 250.degree. F.) prior to an initial cooking, moisture from cooking product may settle in this zone during a cooking cycle. At the end of the cooking cycle when pressure is released, moisture is then cooked or boiled off causing eruption or boiling in the vat. This boiling action stirs up crumb sediment or cracklings and can allow sediment to deposit on the next food product. The following food products may then assume an undesirable taste due to the cracklings and sediment.
The transition zone problem occurs primarily on the first cooking cycle after initial activation of the cooking vessel or after a delay during which time the transition zone may cool. After the first cooking cycle of the day or after a first cooking cycles after a long delay, the normal turbulence of the cook zone and the boiling of the cook zone penetrates the transition zone to the extent that the oil has been mixed and reached a sufficient temperature (e.g., about 250.degree. F.).